The present invention relates to superconducting techniques, and more specifically, to a trilayer Josephson junction with a small air bridge and no interlevel dielectric for superconducting qubits.
In one approach called circuit quantum electrodynamics, quantum computing employs active superconducting devices called qubits to manipulate and store quantum information, and resonators (e.g., as a two-dimensional (2D) planar waveguide or as a three-dimensional (3D) microwave cavity) to read out and facilitate interaction among qubits. Each superconducting qubit comprises one or more Josephson junctions shunted by capacitors in parallel with the junctions. The qubits are capacitively coupled to 2D or 3D microwave cavities. The energy associated with the qubit resides in the electromagnetic fields around the Josephson junction and especially in the vicinity of relatively larger shunt capacitance structures. To date, a major focus has been on improving lifetimes of the qubits in order to allow calculations (i.e., manipulation and readout) to take place before the information is lost to decoherence of the qubits. Currently, superconducting qubit coherence times can be as high as 100 microseconds, and efforts are being made to increase the coherence times. One area of research with respect to increasing coherence times is focused on eliminating lossy materials from areas of relatively high electromagnetic field energy density such as in the vicinity of sharp corners and edges of the thin films of which the qubits are comprised. Such materials in proximity to the qubit can include imperfections that support defects known as two-level systems (TLSs).